Converters, particularly multi-level converters, are increasingly used for performing power conversion in a wide range of applications due to the advantages of high power quality waveform and high voltage capability. For example, multi-level converters may be used for performing DC-to-AC power conversion to supply single-phase or multi-phase AC voltages to electric motors in vehicles and pumps. Multi-level converters may also be used in power generation systems such as wind turbine generators and solar panels for performing DC-to-AC power conversion to supply single-phase or multi-phase AC voltages for power grid transmission and distribution.
Typically, the converters or the multi-level converters may include a plurality of switching elements/devices such as insulated gate bipolar transistors (IGBTs) and integrated gate commutated thyristors (IGCTs) which can be switched on and off in response to pulse signals supplied thereto. The IGBTs and IGCTs are semiconductor devices that are sensitive to electrical current flowing through the IGBTs/IGCTs. To prevent the IGBTs/IGCTs from being damaged by an over current, the IGBTs/IGCTs are typically provided with an over-current protection function. Conventionally, to simplify the implementation of the over-current protection function, an over-current threshold value is set to have a fixed value according to estimations in worst-case scenarios. The IGBTs/IGCTs can be turned off or shut down once the electrical current flowing through the switching element is determined to be exceeding the fixed over-current threshold value. However, simplified implementation of the over-current protection may result in an inadequate utilization of the capability of the converter.
Therefore, it is desirable to provide systems and methods for improved over-current protection to address one or more of the above-mentioned limitations of current systems and methods.